(In reply to comment #7)
> Could you explain in the bug what <hgroup> is and why we would want it?
Because it is defined in HTML5.
http://www.w3.org/TR/html5/semantics.html#the-hgroup-element
Though I feel the benefit of <hgroup>is less than other sectioning elements such as <section> <article> we already have, the example in the specification is reasonable and <hgroup> is not harmful.